Motor-control system



H. D. JAMES.

MOTOR CONTROL SYSTEM.

APPLICATION FILED NOV. 5. 1920.

1 ,425,657, Patented Aug. 15, 1922.

WITNESSES: -|NVENTOR flemy .D. James m BY 77 00251111 l Q ATTORNEY UNITED STATES nmmr n. sums, or nnoswoonrm,

HOUSE ELECTBIOfi IAN'UI'AGTUBING comm,

VANIA.

Specification 01' Letters latent.

PATENT OFFICE, Y

lco'lron-oon'ritor. s'rs'rmk.

Application ma November 5, 1920'. serial Io. mesa- Toallwhomitma-y concerwr Be it known that Igl Hans! D. J AMEB,- a citizen of the United States, and a resident of Edgewood Park i'nlthe county of Allegheny and State of Bennsylvania, have invented a new and useful-Improvement in' Motor-Control Systems, of which the following is a specification. f

My invention relates to motor-control systems and it has particular relation to motors employed to operate. skip hoists, especially those that are subjected tofvari'able loads. One of the objects of my invention is to -v provide an automatic device wh-iclf will liree ow l6 vent a" skip of a hoist from traveling b a sredetermined speed, especially near the on of its 'ourney.

In actual practice,.'for satisfacto' operation it is necessary to operate the 5 ip at a fixed speed near the top and bottom of the hoist in such manner that the track: limit switches will stop the ski at the proper point. It is diflicult to a resistors to compensate for difierent loads such, for-e11:- arf) e, r V

o er to maintain the motor at' a certa n speed, when the skip is near the'top or bottom of a hoist, with variable leads, an automatic device must be employed to compenso sate for loads of difierent weights.

By means of my invention it will be pose sible'for' the tracklimit sw tches to bring the controller to the position for effecting relatively slow operation of a'motor, when the skip is near the end of its travel, and,

if the speed of the skip falls below a 'predetermined value, an automatic device will cause the motor to increase its speed.

Briefly eaking, my invention consists in so controll ng a contactor for shuntinga resistor that is connected in series with the field-magnet winding of a motor, that the contactcr will be automatically opened by m device when the speed of the motor falls 46 be ow a predetermined value and closed upon the speed of ater than this value.

For a better understanding of my invention, referenaefshould be made to the accom anymg" rawmg Figure 1 of which is a diagrammatic view as coke, limestone, and iron ore; In

the motor becoming Patented Au 15, 1622.

of a motor-control system embodying invention; 1

Fig.2 18 a schematic view of themotorcontrol system shown in Fig; 1;

Fig. 3 isa sequence chart of well-'ltnown form for the contactors shown in and 2;

Fig. 4 is artl'y in section, of apparatus employed in 1%:Llflld 1 1g. 5 is a schematic view of a modified a view, partly in elevation and Q form of control system embodying my invention.

Referrin particularly to Figs. land 2, a motor 1, avin an armature flandashufit field magnet win ing 3','is energized through a circuit corn and a circuitreaker 5. A shunt resistor 6, which is also employed for dynamie'bi'llk llifi may be electrically connected in pera e A resistor 9 is connected in s rigs-m1; tion with the shunt field-magnet winding 3 A starting resistor 10 isconnected in series relation to the armature 20f the motor Q 1 by a contactor 7.

relation with the armature 2 of the motor;

1', and portions of the resistor may be shunt;

ed by accelerating conta'ctors 11 and212. A master controller 15 governs the operation of" the coptactors 7, 11 and 12 and of the circuit breaker 5. A speed-control device 16' is mechanically connected to the armature 2 ofthe motor 1 by a shaft 17 that is providedwith a pulley 18 and a belt is constructed in accordance with the invention of Stephen'A. Stae e, as set forth in a copending application, erial No. 29%, filed May 15 1919, and assigned to the estinghouse Electric & Manufacturing 'Com-.

e master controller 15 has an ofi po- 1 sition and three .0 rating positions, a, b

"and c. The contro or 15 may be any welle motor 21 drives a shaft 22 a pinion Q3. The pmd from any suitable source at 19 that is mounted thereon. The device 16 ion 23 actuates a bevel-gear member 24, which is rotatably mounted upon the shaft 25. The belt 19 actuates a bevel gear member 26 which is also rotatably mounted upon the shaft 25.

Between the gear members 25 and 26 is a disk member 27, which is likewise rotatably inounted upon the shaft 25. The member 27 has a plurality of pinions 28 rotatabl mounted thereon by means of pins 29. he pinions 28 are tated by the bevel-gear mem rs 24 and 26. A metal band or strip 31 surrounds the central member 27 and is maintained in frictional enga ement therewith by means of a bolt 32 on w ich is mounted a resilient member, such as a helical spring 33, a washer 34, and a nut 35. The bolt 32 is slidably mounted in a stationary slotted member or bar 36.

A contact member 37 is rigidly mounted upon the bolt 32 and may be brought into enga ement with the stationary contact tenminai 38. The belt 19 moves in the direction shown by the arrows when the armature 2 of the motor 1 is operating to raise the skip. Ths causes the bevel-gear .member 26 to rotate in a counter-clockwise direction. The bevel-gear member 24 is actuated in a clockwise direction b the pinion 23 of the motor 21. The spec and direc: tion of the central rotatable member 27 is then determined by the difference in speed of the beveled gear members 24 and 26.

When the motor is operating above a predetermined speed, the movable contact member 37 enga s a stationar contact terminal 38, but if t e s eed of the armature 2 so decreases that tlib belt 19 drives the bevelgear member 26 below the s eed of the bevel gear member 24, the centre rotatable meme ber 27 will turn in a clockwise direction until the contact terminal 38 is no lon er engaged by the movable contact mem er 37.

he ogleration of the motor 1 is begun by closing 1; e knife-blade switch 4 and actuating the controller 15 from its off position to the initial hoist position a. When the master controller 15 occupies position a, a circuit is established from supply conductor 39 through knife-blade switch 4, conductors track-limit switch 41, contact terminal 42, contact segment 43 of the master controller 15, contact terminals 46, conductor 47, actuating coil 48, conductors 49 and 50, and knife-blade switch 4, to supply conductor 51'. When,this circuit is established, the actuating coil 48 is energized, thereby closing the circuit-breaker 5 The actuating coil 48 of the circuitbre'aker 5, being thus energized, causes the circuit-breaker 5 to assume its closed position, thereby establishing a circuit from conductor 40 through circuit breaker 5, armature 2 of the motor 1, and starting resistor engaged and ro-' 40 and 41,.

A shunt cirthe armature comprising shunt resistor 6 10 to negative conductor 50. cuit is also established around 2'by' a circuit and contactor 7.

When the master controller 15 is actuated to its second position b, a circuit is established from contact segment 43 through contact terminal 53, conductor 54, actuating coil 55 of the contactor 7 and conductors 56 to return conductor 50. The actuating coil 55, being thus energized, causesthe contactor 7 to assume its 0 en position.

In addition, when the master controller 15 is in its second position 6, contact segment 43 engages contact terminal 60, thereby establishing a circuit comprising the actuating coil of the contactor 11. The actuating coil of the contactor 11, being connected across the armature 2, will be energized in accordance with the counter-electromotive force of the motor 1. When the counter-electromotive force is suflicient to close the contactor 11, a portion of the startin resistor 10 is thereby shunted.

TV'hen the master controller 15 is actuated to its third position 0, contact se ment 43 en ages contact terminal 64, there y establisfiin the circuit comprising the actuating coil 0 the accelerating contactor 12. The contactor 12 is subsequently closed by the counter-electromotive force of the motor 1, thereby shunting the entire starting resistor 1.0. If the master controller 15 has onlya single osition, such as c, for forward operation, t e acceleratin contactors 11' and 12 may be adjusted to c ose in roper sequence, in accordance with a well-linown practice.

The motor 1 will now 0 erate at its maximum speed for the load t at it is carrylng. The skip will ascend at the correspondi speed until it arrives at a point where 1t operates the track limit switch 41, whlch will stop the motor 1 by opening contactors 5, 11 and 12 and closing contactor 7. A dynamic braking circuit is thus formed through the shunt resistor 6 and contact/or 7.

It is, of course, a parent to those slnlled in the art, that, if t e resistor 6 is adjusted to reduce the speed of the motor 1 to a relatively low "alue with a light load, such, for example, as coke, the motor 1 may come to a stop with a maximum load, such, for example, as iron ore; for a greater portion of the current will then flow through the shunt resistor 6.

If there is no compensating means provided the ski will stop prematurely, when it is tilled wit iron ore, or, at least it will travel below a safe and desirable speed. It is to avoid such occurrences that I have devised the resent control system.

When the armature 2 travels above a predetermined speed, the contact member 37 enmg a circuit from conductor 40 through conof contactor 69 is ener med, thereby closing the contactor 69 and s unting the field-circuit resistor 9. The speed of the motor 1 will be reduced, since the energizationof the field-magnet winding 3 is thus increased.

If the armature 2 of the motor l travels below a predetermined speed, the bevel-gear member 26 will rotate at a slower speed than the speed of the' bevel-gear member 24, thereby causing the central rotatable member 27 to rotate in a clockwise direction and thus separating the contact member 37 from the contact terminal ,38. Under this condition, the actuating coil 68 of the contactor 69 is de-energized, thereby allowing the contactor 69 to open.

When the contactor 69 is open, the fieldcircuit resistor 9 is connected in series relation with the shunt field magnet winding 3 thereby lessening the excitation thereof an thus causing the motor 1 to increase its speed.

In the modification shown in Fig. 5, a contactor 71, corresponding somewhat to the contactor 69, normally shunts a portion of the shunt or dynamle braking resistor 6. When the speed of the motor 1 falls below a predetermined value the contactor 71 opens, thereby inserting more resistance in the shunt circuit around the armature 2 of the motor 1, thus causing a reater current to traverse the armature 2. he motor speed is thereby increased to the desired value.

Directional or reversing contactors for the motor 1 have been purposely omitted because they are well-known in the art. Track limit switches to prevent over-travel of the skip have not been shown in detail for the same reason.

By the employment of my invention, it is possible to operate a skip hoist with greater efficiency than in the past for the weights of the vari'ous loads carried by the skips will not change the speed of the motor. T e skip speed will not vary greatly from a predetermined value consistent with safety, until the track limit switches and the automatic brakes (not shown?l operate to stop the skip.

While I have s own my invention in a preferred form it is apparent that modifications may be made in the apparatus employed and arrangements of circuits without eparting from t e spirit thereof. I desire, therefore, to be limited only by the scope of the a pended claims.

I c aim as my invention:

1. In a motor-control system, the combination with a motor and means for normally controlling the s eed of said motor, and means for effecting electrical braking of said motor, of automatic means for restoring for controlling the current motor changin the speed of said motor upon the speed thereof departing from a predetermined value during electrical braking.

2. In a motor-control system the combination with a motor and means for normally controlling the speed of said motor, of means for efi'ecting dynamic floraking of said motor, and automatic means comprising an auxiliary motor and a differential gear mechanism driven by said auxiliary motor for acceleratin said main motor main motor falling upon the speed of sai below a predetermined value during dynamic braking of said motor, and for decreasing the motor speed when it increases above a fixed value.

3. In a motor-control system the combination with a main motor an means for normally controlling the speed of said main motor, of means for effecting electrical braking of said motor, and automatic means comprising an auxiliar motor and a differential gear mechanism driven by said main and said auxiliary motor for accelerating said main motor upon the speed of said main motor falling below a redetermined value during electrical braking.

4. In a motor-control system, the combination with a motor and means for control ling the energization of said motor, of automatic means for effecting electrical braking of said motor, and automatic means for restorin the speed of said motor upon said contro ling means being so operated that the speed of said motor de arts from a redetermined value during e ectrical braking.

5. In a motor-control system, the combination with a motor, having an armature and a field magnet winding, and means for controlling the current flow through said armature, of automatic means for effecting dynamic braking of said motor, and automatic means for diminishing the excitation of said field-magnet windin upon the speed of said motor decreasing low a predetermined value during dynamic braking.

6. In a motor-control system, the combination with a main motor having an armature and a field-magnet windin and means ow through said armature, of means for effecting electrical brakin of said motor, an auxiliary motor, a di erential gear having the end members thereof, respectively, rotated by said main and said auxilia motor, and means controlled by said di erential ear for varying the voltage across said eld magnet winding upon the speed of said more than a predetermined value during e ectrical braking.

7. In a motor-control system, the combination with a main motor having an armature and a field-magnet winding, and a resistor, of a contactor for connecting said resistor in parallel relation to the armature of said motor, a controller for operatin said of an automatic device controlled b the 80 contactor, a field resistor in series re ation speed of said motor for operating sai mewith said field-ma et winding, a contactor tor at substantially constant speed during forshunting said eld resistor, an auxiliary electrical braking. 1 7

motor, a differential gear having the end 11. The combination with a motor submembers thereof, respectivel rotated by jected to variable loads and means for ef- 85 said main motor and said auxilia motor, fecting dynamic braking of said motor, of and means controlled by said di erential' an automatic device for increasin the d gear for controlling the operation of; said of said motor u on said speed fal ing below shunting contactor. a predetermin value durlng dynamic brak- 8. The combination with a motor, .and ing, said means reducing the speed of said 4c means comprising a controller having a plumotor upon said s eed becoming greater rality of positions for normally operatin' than a predetermined value. and controlling the speed of said motor, 0% 12. The combination with a motor subject automatic means adapted to partially oomto variable loads, said motor having a fieldpensate for an excessive variation in speed magnet winding, of means for varying the 45 of said motor upon said controller being excitation of and windin during dynamic actuated to an inoperative position. braking, and an automatic device com ris- 9. The combination with a motor subject ing a member controlled b the spec of to variable loads, and a controller having an said motor for operating sai means to raise off position and an cgperative position, of or lower the speed of said motor upon said 50 an automatic device or maintaining the motor varyin its speed below"0r above a speed of said motor at a substantially conpredetermine value during dynamic brakstant value for a period of time after said in controller has been actuated toits ofi' po- Tn testimqny whereof, I have hereunto sition, regardless of the variation in weight subscribed my name this 22nd day of Octo- 55 of said loads. ber 1920. i

10. The combination with a motor sub'ect to variable loads during electrical braking, HENRY D. JAMES. 

